The present invention relates to a lock mechanism for mounting to a door or a door frame wherein the door will control access to a secured area. More particularly, the present invention relates to a lock mechanism having incorporated therein a knob control arrangement which permits a knob member for the lock mechanism to be rendered active or passive, at the selection of an operation from exteriorly of the lock mechanism, such that when in the passive condition, the knob member or members can rotate freely without imparting motion or placing strain upon the internal components of the lock mechanism, and when in the active condition, rotation or movement of the knob members will effect operation of the lock mechanism.
There are many instances wherein it is desirable to be able to control selectively access to a secured area by means of the lock mechanism used on the door leading to said area. And to this end, to effect this control exteriorly of the lock mechanism by selectively rendering the knob or operating member operable or inoperable with respect to the internal components of the lock. The basic components of most lock mechanisms do not vary to a great extent, in that these mechanisms normally include some form of latch member, an external operating member, such as a knob, that is coupled for relative movement with respect to the lock mechanism, and various internal cams and link members for converting movement of the operating member into operation of the latch member. The normally accepted procedure in effecting this control involves utilization of some form of latch or blocking means internally of the lock mechanism which is engageable with one or more of the internal cams or link members to prevent or block movement thereof. An example of this type of control means can be found in the inventor's prior U.S. Pat. No. 4,237,711 issued Dec. 9, 1980 and entitled "LOCK MECHANISMS." In the embodiment illustrated therein, solenoid operated latches are used selectively to block the operation of a cam member or roll back to which the external knob member is affixed.
While the above specifically discussed prior art arrangement has proven satisfactory for numerous uses, it is subject to certain disadvantages. More specifically, with this and other types of knob control arrangements wherein operability of the knob is controlled from the exterior of the housing, the knob is always in an active state. That is to say, the external knob or operating member is operably connected with the internal latch mechanism at all times, such that rotation of the knob will result in operation of the latch mechanism. To render the knob inoperable, operation of the knob is merely blocked by some form of internal latch mechanism. As such, one trying to operate the lock can place considerable force on the knob, and correspondingly, upon the internal mechanism of the lock, especially the components of the internal latch mechanism. The force placed thereon could become extensive enough to overcome the blocking operation through damage or failure of the internal latch and lock mechanism.
With the present invention, a knob-control system or arrangement is provided such that when it is desired to render the knob mechanism inoperative, this is achieved by producing a passive condition for the knob. That is to say, when the inoperative-passive condition is achieved, the knob is not operatively connected to the internal components of the lock mechanism, and as such is free to rotate without placing any force or strain on said internal components. The active-operable condition for the knob is achieved by selective coupling of the knob to the internal mechanism such that knob movement will affect operation of the internal mechanism to retract the latch bolt as desired. As such, with the present invention it is possible to control the operation of the lock mechanism from a remote location or exteriorly of the lock, such that when it is in the passive-inoperative condition, any attempt at operating the lock via the knob or knobs will not result in the placement of stress or strain on the internal lock components. As such, the lock cannot be forced by placing stress upon the internal mechanism to overcome the blocking arrangement.
As will be discussed more fully with regard to the detailed description of the disclosed embodiment which follows, there is shown two specific embodiments of the present invention. In the first embodiment, the overall knob control arrangement utilizes a solenoid for effecting operation of the control means for rendering the knob passive or active, as desired. In the second illustrated embodiment a novel linkage arrangement is employed in conjunction with the basic knob control system. Which linkage arrangement as illustrated is key actuated via the cam member of a lock set carried by the lock housing. As a further matter, with regard to the utilization of a solenoid to affect actuation of the knob control arrangement, the system can be made "fail-safe" or "fail-secure" as desired. More specifically in this regard, the solenoid employed could be of the type such that upon disruption of power, whether intentionally or due to a power failure, the knob will automatically be placed in the active or operable condition, thus achieving a "fail-safe" condition. On the other hand, the solenoid arrangement may be such that upon a disruption of power, the passive-inoperative condition is achieved so that attempts to operate the knob will not result in operation, thereby rendering the unit "fail-secure.